Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

The "Non-Destructive Guillotine" ("NDG") Scanner

Built a scanner? Started to build a scanner? Record your progress here. Doesn't need to be a whole scanner - triggers and other parts are fine. Commercial scanners are fine too.
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jlev
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The "Non-Destructive Guillotine" ("NDG") Scanner

Post by jlev » 22 Apr 2016, 04:39

It's been six years since I built my first scanner. I got interested again in the topic last fall, and have been lurking here since, reading up on the developments of the community. I'm excited to share what I think is a new design: I call it the "Non-Destructive Guillotine," because it features a vertically-sliding platen (like a guillotine) but doesn't involve cutting the spines off of the books to be scanned.

I had three goals with this design:
  1. It needed to be inexpensive to build (preferably for less than $100 in parts, plus the cost of a single camera).
  2. It needed to be able to fit into a backpack or other small carrying case (I built another scanner in November 2015, which I'll post about in the future, which was over-engineered and is too large to fit even into a suitcase).
  3. Preferably, it needed to be able to be built without power tools. Although I have a tool collection now, when I was an undergraduate, I only had access to a power drill (no circular saws, drill presses, etc.). Thus, building a scanner as an undergraduate was made difficult mostly by my inability cut materials such as wood without help. I wanted this build to be accessible to my younger self – something, for example, that a group of students living in dormitories or studio apartments could build and share.
The scanner uses a single camera to take intentionally-keystoned photographs of each two pages in a book, held open at a 90-degree angle to one another (thus, each page is 45 degrees off from the camera). The scanner features a trolley system to lower the camera as the book is scanned, causing the keystoned pages at every point of the book to stay in the same spatial relationship with the camera. This allows the photographs of all pages to be de-keystoned in a batch, using software such as Darktable. In addition to hardcover books, the scanner also works well with paperback books and magazines: the folding/hinged nature of the platen makes it impossible for tightly-bound books to snap shut before the operator can intervene. The design is especially inspired by David Landin, whose idea to use PVC plumbing pipe was in itself (in addition to his approachable, highly-functional scanner design), I think, a major development in the community.

This build uses what in the USA is called "Schedule 40" 3/4-inch PVC pipe. It's thicker than normal PVC, and thus doesn't need to be glued together to be structurally stable. This makes it ideal for a project like this, since it can be (1) easily disassembled, and (2) easily expanded (it would be trivial, for example, to add additional lighting arms to this build, or arms on which to hang a black drape).

A video of the scanner's construction and use is here: https://www.youtube.com/watch?v=MkwZCIYd0pg. Below are some photos of the scanner (without my camera attached) and sample images from an out-of-copyright book:

In addition, I've published a full parts list, price list, and cut list (for cutting down the PVC and other materials), here: http://adunumdatum.org/an-introduction- ... anner.html (I'd be happy to re-publish them here, as well).
Full_Scanner_Front_Angle.jpg
Full scanner, front angle.
Full_Scanner_Right-Side_Angle.jpg
Full scanner, right-side angle.
Full_Scanner_Rear_Angle.jpg
Full scanner, rear angle. Note that the metal mending plates at the top of the platen *should* be folded out, such that they make the platen unable to move further forward than the PVC columns.
Full_Scanner_Left-Side_Angle.jpg
Full scanner, left-side angle.
Camera_Trolley_Detail_1.jpg
The camera trolley, which uses a paracord-based pully system to keep the camera in spatial synchrony with the platen.
Table_of_Parts_2.jpg
The table of parts (everything fits into a backpack).
original_page_image.jpg
Original image.
processed_page_image.jpg
Processed image.
The scanner design is released into the Public Domain via a CC0 dedication.

duerig
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Re: The "Non-Destructive Guillotine" ("NDG") Scanner

Post by duerig » 22 Apr 2016, 11:38

This looks awesome. For comparison, I recently saw a prototype mobile scanner using 14 MP camera sensors being shown off by a professional book scanning company. When I asked, the representative said that it would cost $10,000 per unit. So it looks like you've managed to shave a couple of orders of magnitude off of the price. :-)

A few questions:

(1) How does the paracord camera positioning system work? Having a fixed geometric relationship between the camera and the platen makes a lot of things better, but usually this is done by fixing both of them on the frame and moving the book. You seem to have hit upon a method that moves them both but keeps them in synch. I can't quite visualize how you've got it working.

(2) I really like that this is both mobile and works well for small books. This is an area where my own scanner falls down completely. For small paperbacks, they flip closed with every page turns. And a 40 pound 4-foot tall monster is not exactly portable.

Can you show how the platen works for small books? I'd love to see a video where a few pages are scanned so I see exactly how your hinged platen works out.

How long does it take to assemble/disassemble? Is there any finicky callibration that has to be done? Could you imagine this being taken to a library or job site and being assembled for a few hours or scanning?

(3) Looking at your sample image, the text seems to be compressed horizontally which may be an artifact of the de-keystoning. Is that true, or is the book in a narrower than normal font? Have you tried different camera setups with your rig to remove the need for de-keystoning? For example having a single camera looking down vertically and scanning just one page at once? Or even having two cameras, one horizontal and one vertical?

(4) Do you have any problems with lighting uniformity? You mentioned that it is trivial to make longer arms to put the lights further away from the book. Do you anticipate needing to?

Thanks for sharing. This design definitely gives me some food for thought.

-D

jlev
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Re: The "Non-Destructive Guillotine" ("NDG") Scanner

Post by jlev » 22 Apr 2016, 17:36

duerig, thanks for your kind words! I hugely respect the work that you've been doing with the Archivist and Archivist Quill, as well as moderating the community now.
I recently saw a prototype mobile scanner using 14 MP camera sensors being shown off by a professional book scanning company. When I asked, the representative said that it would cost $10,000 per unit. So it looks like you've managed to shave a couple of orders of magnitude off of the price.
I decided to use a single-camera scanner so that I could spend more money on one really nice camera, rather than less money on two not-so-nice cameras. I bought a Panasonic Lumix G5 mirrorless camera for $250 on ebay; it's 16MP and has a sensor that's as large as any DSLR (so better than a point-and-shoot). The camera is certainly an additional cost, but, as you said, it's still less than the commercial options that are out there. :) Plus, it's possible to use the camera for other purposes while not scanning.
(1) How does the paracord camera positioning system work? Having a fixed geometric relationship between the camera and the platen makes a lot of things better, but usually this is done by fixing both of them on the frame and moving the book. You seem to have hit upon a method that moves them both but keeps them in synch. I can't quite visualize how you've got it working.
The book's pages are on two planes: the right-side pages are horizontal, while the left-side pages are vertical. The vertical pages are always kept in the same spatial position by the platen, which is designed so that it can't move forward of the PVC columns (thus, as the operator turns more pages, the left-side cover moves back more and more relative to the platen – the pages are always in the same place).

For the right-side pages, I realized that for a thick book, the pages at the beginning of a book are higher (and thus on a slightly different plane for de-keystoning) than the pages at the end of the book. Thus, I connected the platen and the camera mount via a pulley system. The pulley goes up from the top of the platen, over the top and then under the bottom of the frame, and then attaches to the camera trolley. The camera trolley is positioned at the beginning of a book so that when the platen is down on the book's first page, the paracord is taut. As the user then scans the pages, and the platen drops vertically slightly more and more with each page turn, the paracord pulls the camera trolley down correspondingly (bit-by-bit with each page turn). Thus, from the camera's perspective, the left-side pages are always in exactly the same position, as well. This allows de-keystoning the entire book using Darktable or similar software at once. Is that making more sense, as I'm explaining it now? (I've included a timecode link to the video demo. below, too, in case it would help to see it in action.)
(2) I really like that this is both mobile and works well for small books. This is an area where my own scanner falls down completely. For small paperbacks, they flip closed with every page turns. And a 40 pound 4-foot tall monster is not exactly portable. Can you show how the platen works for small books? I'd love to see a video where a few pages are scanned so I see exactly how your hinged platen works out.
In the video here, at 25:03, I demonstrate the scanner's usage (including the folding platen). There's a full-speed demo at 28:26 in the video. As the video shows, one improvement for the design would be for the platen to be on an actual track system.

The platen is just hinged with a thin strip of transparent packing tape. I was surprised that this actually seems totally durable enough for use.
How long does it take to assemble/disassemble? Is there any finicky calibration that has to be done? Could you imagine this being taken to a library or job site and being assembled for a few hours or scanning?
One of my main goals with this build was to allow easy transport and storage (I haven't made a post about it yet, but I made another single-camera design last November out of PVC, which mechanically replicated all of the features of an overhead scanner like the one in this picture. But it takes up an entire table, and can't fit even into the largest suitcase I could find.

This newer design fits into a backpack. I timed myself, and it takes ~7 min. to set up. The only calibration that's needed is (1) making sure the lighting isn't producing glare, and (2) adjusting two wingnuts on the camera trolley so that the trolley doesn't move under the weight of the camera, but responds to light pulls from the pulley system.
Backpack2.jpg
Backpack1.jpg
(3) Looking at your sample image, the text seems to be compressed horizontally which may be an artifact of the de-keystoning. Is that true, or is the book in a narrower than normal font?
I think that the font for the book is slightly narrower than normal (the book is an antique, from ~1910; having said that, I also think that the de-keystoning process is prone to subtle artifacts. When the user gets it right, it looks great; it's easy, though, to be even slightly off when de-keystoning in Darktable, which can produce it-doesn't-look-quite-right types of errors like in the example image I posted. One addition I'm considering to fix this is to place something like brightly-colored calibration dots on the platen at the corners of each book, to always have consistent reference points to use when de-keystoning.

Here's a photo face-on to the original page (low quality, from my phone, but something to show what the font actually looks like):
Page_taken_with_Phone.jpg
Have you tried different camera setups with your rig to remove the need for de-keystoning? For example having a single camera looking down vertically and scanning just one page at once? Or even having two cameras, one horizontal and one vertical?
One of the things that I love about using PVC (and specifically Schedule 40 3/4-inch PVC) for this type of project is that it's much more versatile than materials like wood, for example. The user could slide the camera mount off of the vertical arm and re-attach it to the horizontal arm that goes over the top of the scanner, making a type of copy stand. That's actually almost exactly what I did recently; I was helping to archive a series of magazine covers, including this one (from Ms. magazine), which I think turned out well:
Ms._magazine_Cover_-_Spring_2016.jpg
I haven't tried using two cameras, but could see the setup working well with that approach – one would just need to add a second camera mount to the top, and move the existing camera mount lower on the PVC column it's already attached to.
(4) Do you have any problems with lighting uniformity? You mentioned that it is trivial to make longer arms to put the lights further away from the book. Do you anticipate needing to?
I am still trying to dial in the lighting. The arm length I've used is the shortest amount needed to get the lightbulbs out of the way of the platen, such that they're not reflecting into the camera. I've found that the lighting is uniform-ish with the current setup: with black-and-white books, the text comes out crisp (especially after sharpening the images slightly in Darktable before sending them into ScanTailor); for color books (especially art books that are larger), the lighting at the edges can sometimes be unevenly bright. So I'm still working on this aspect, and would love suggestions from anyone in the community. I'm also probably not using the best bulbs for scanning: two 1600-lumen 5000K (white-light) CFLs.

Thank you for your questions; your interest means a lot to me!

duerig
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Re: The "Non-Destructive Guillotine" ("NDG") Scanner

Post by duerig » 25 Apr 2016, 00:39

I've watched your video and this scanner has been in the back of my head this weekend while I've been working on other stuff. So I have two more thoughts.

First, T-slot aluminum extrusion is versatile in many of the same ways that PVC pipe is. And I happen to have a bunch of it lying around. It would be fun to try to make a similar design from T-Slot.

Second, you mention that it would be nice for the hinged platen to slide up and down in a slot. T-Slot is perfect for this. You have two vertical columns spaced apart right and suddenly you have constrained the platen in a slot.

Third, I think there may be a way to make it so that the camera doesn't need to move any more. Suppose that instead of the cradle resting on a hard surface it rested on a spring box. Something like those plate dispensers at a buffet. Then you have a stop in the platen slot so that the top of the platen hinge always stops on the same side. And you have another stop for the bottom of the platen hinge so it always stops at a 90 degree angle. And now you have a moving platen that always stops in the same place when you scan a book. This means that the camera(s) can stay in the same place.

What do you think? Would this be more complicated than the paracord solution you have working now? It is certainly simpler than the paracord for two cameras.

If I get time, I may tinker with this some myself. The idea of figuring out how to make a mobile scanner that is much cheaper is very appealing to me. And your scanner design opens up some new avenues.

-D

jlev
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Re: The "Non-Destructive Guillotine" ("NDG") Scanner

Post by jlev » 29 Apr 2016, 17:22

First, T-slot aluminum extrusion is versatile in many of the same ways that PVC pipe is. And I happen to have a bunch of it lying around. It would be fun to try to make a similar design from T-Slot.
I've never used T-slot nor seen it in action beyond your work on the Archivist Quill and assorted forum posts here. I'd love to see what you come up with from this! How does the price of T-slot extrusion compare to PVC? What about weight?
Second, you mention that it would be nice for the hinged platen to slide up and down in a slot. T-Slot is perfect for this. You have two vertical columns spaced apart right and suddenly you have constrained the platen in a slot.
I agree that this type of track system would be an improvement on the current design. The PVC frame could be further pared down if it were re-made using T-slot, such that the lighting arms that currently come out of the "spine" of the scanner could be replaced with attachments on those two vertical columns, as well. The cradle could slide laterally on a similar track (replacing the PVC spine with 1-2 pieces of T-slot). Is that keeping with what you have in mind?
Third, I think there may be a way to make it so that the camera doesn't need to move any more. Suppose that instead of the cradle resting on a hard surface it rested on a spring box. Something like those plate dispensers at a buffet. Then you have a stop in the platen slot so that the top of the platen hinge always stops on the same side. And you have another stop for the bottom of the platen hinge so it always stops at a 90 degree angle. And now you have a moving platen that always stops in the same place when you scan a book. This means that the camera(s) can stay in the same place.
This sounds reasonable to me. The two concerns that occur to me are (1) that the strength of the springs would need to be low enough that it wouldn't contribute to operator fatigue, and (2) that a spring box might be bulkier (and thus less portable) than the pulley design. These are both empirical concerns, though – they could both be answered with trial and error.
What do you think? Would this be more complicated than the paracord solution you have working now? It is certainly simpler than the paracord for two cameras.
The paracord system has the advantage of being more-portable (it's just paracord and a camera mount), at the cost of requiring some configuration (getting the mount adjusted to the weight of the camera). For a first iteration with T-slot, then, I'd suggest keeping the paracord while adding the platen track, since the platen track would pretty definitely immediately increase smoothness of operation. Then a spring box could be added subsequently. (I'm assuming that the spring box would take a non-trivial amount of effort to put together; if that's not the case, go for it all at once!)
If I get time, I may tinker with this some myself. The idea of figuring out how to make a mobile scanner that is much cheaper is very appealing to me. And your scanner design opens up some new avenues.
I'm excited to be discussing it; thanks! :)

jlev
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Re: The "Non-Destructive Guillotine" ("NDG") Scanner

Post by jlev » 16 Apr 2017, 00:32

For archival purposes, I've attached a PDF version of the blog post listed in my original post above.

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Re: The "Non-Destructive Guillotine" ("NDG") Scanner

Post by daniel_reetz » 13 Aug 2017, 10:19

Good to see you 'round these parts, jlev!

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